The online company Currency Express have the best rate at the moment, but to be honest the Euro is quite strong just now so it ain't gonna make a great deal of difference.
If you do get them from travelex don't get them on the day over the counter,
as there over the counter rate is not as good as the pre-booked online rate.
thanks for the advice guys-forgot about this thread and have only just looked at it! Have gone with Travelex and picking them up from the airport. Seemed the best rate.. thanks